Percentage Calculator
Work out a percentage of a number, what percent one number is of another, and percentage increase or decrease.
Content updated July 1, 2026
Percentages come up everywhere — discounts, tips, tax, grades, interest, statistics — and it's easy to blank on which number to divide by. This calculator handles the three questions people ask most, each with a plain-English answer and the working shown.
Pick the type of calculation, enter your two numbers, and get the result instantly. No formulas to remember.
The Percentage formula
X% of Y = (X ÷ 100) × Y; X is (X ÷ Y × 100)% of Y; % change = (new − old) ÷ old × 100X = the percentage or part · Y = the whole or base value · old and new = the values before and after a change. A positive % change is an increase, a negative one a decrease.
Worked example
20% of 150 is (20 ÷ 100) × 150 = 30. The other way round, 30 out of 150 is 30 ÷ 150 × 100 = 20%. And a price rising from 150 to 180 is a (180 − 150) ÷ 150 × 100 = 20% increase.
The three common percentage questions
‘What is X% of Y?’ multiplies: for example 20% of 150 is 0.20 × 150 = 30. Use it for discounts, tips, and tax.
‘X is what percent of Y?’ divides then multiplies by 100: 30 out of 150 is (30 ÷ 150) × 100 = 20%. Use it for scores, shares, and proportions.
‘Percentage increase or decrease’ compares an old and new value: (new − old) ÷ old × 100. A rise from 150 to 180 is a 20% increase; a fall to 120 is a 20% decrease.
Frequently asked questions
▶How do I calculate a percentage of a number?
Multiply the number by the percentage divided by 100. For 15% of 80: 80 × (15 ÷ 100) = 12. The 'percent of a number' mode above does this for you.
▶How do I work out percentage increase?
Subtract the original value from the new value, divide by the original value, and multiply by 100. From 200 to 250 is (250 − 200) ÷ 200 × 100 = 25%.
▶How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. So 45 out of 60 is (45 ÷ 60) × 100 = 75%. The 'X is what percent of Y' mode above does this for you.
▶How do I calculate percentage decrease?
Use the same formula as an increase: (new − old) ÷ old × 100. If the result is negative it's a decrease. A drop from 80 to 60 is (60 − 80) ÷ 80 × 100 = −25%.
▶How do I add a percentage to a number?
Multiply the number by 1 plus the percentage as a decimal. To add 15% to 200: 200 × 1.15 = 230. To take 15% off, multiply by 0.85 instead.
▶What is the difference between percentage change and percentage points?
A percentage point is a plain difference between two percentages, while percentage change is relative. Going from 10% to 15% is a rise of 5 percentage points, but a 50% increase.
Learn more
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Open calculator →Disclaimer: Percentage Calculator results are estimates for general information and education only, and are not financial, tax, legal or medical advice. Verify important decisions with a qualified professional.